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Project GB4
Structure and dynamics of cold seeps
G. Bohrmann and V. Spieß
A. Boetius, N. Fekete, H. Keil, T. Pichler, T. Pape, H. Sahling
Background
Due to novel, detailed sea- and sub-seafloor imaging techniques, cold seep systems are increasingly being recognized as ubiquitous and prominent features in sedimentary environments at active and passive continental margins. Technological improvements and a significant increase in data quality now resolve structures laterally on meter- and vertically on submeter-scales. It is still unclear which factors control retention or leakage shallow gas in sediment bodies but sediment facies, permeability and grain size, and degree and style of deformation are likely all involved. This uncertainty applies to both the larger scale structural framework of Neogene sediment cover, but also to the shallowest few tens of meters. The project focuses on the physical and geological constraints for the existence of seepage and uses both geophysical survey methods and acoustic water column imaging in conjunction with sample analyses on geologic seep products.
Scientific questions
•Which processes within the gas hydrate stability zone control the presence and distribution of free gas, its upward migration and fluxes to the surface, and how are these processes linked to surface morphologies, seep manifestations, and the nature and distribution of methane release at the sea floor?
•Is there an evolutionary sequence of seep systems or do juvenile and mature seeps coexist on a regional scale?
•Is temporary storage of hydrocarbons as gas hydrate in the shallowest sub-seafloor a prerequisite for large chemosynthetic ecosystems?